JP4174604B2 - Concrete compression test equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a test apparatus for performing a concrete compression test.
[0002]
[Prior art]
The standard of JIS A1108 is known as a concrete compression test method. In this standard, first, the compressive stress (substantially compressive load) acting on the specimen is constant under the constant stress rate control for the concrete block (hereinafter referred to as specimen). The test was performed while controlling the load mechanism so that the speed increased at a constant speed.After the specimen started abrupt deformation, control of the speed at which the load was applied was stopped, and the opening of the servo valve for control was Switching to constant speed stroke control kept constant will continue to apply compression load.
[0003]
In order to satisfy this standard, in the conventional concrete compression tester, the tester visually observes the condition of the specimen, and when a rapid deformation of the specimen is recognized, it is manually controlled from the stress rate control to the constant speed stroke control. It was switched to.
[0004]
[Problems to be solved by the invention]
According to the conventional concrete compression test apparatus and the compression test using the apparatus as described above, the time point for switching from the stress rate control to the constant speed stroke control depends on the judgment of the tester. There is a possibility that mistakes may occur, and it is difficult to say that an accurate test is always performed, and there is a problem that the reliability of the test is lacking.
[0005]
The present invention has been made in view of such circumstances, and switching from stress rate control to constant speed stroke control can always be performed accurately in accordance with the standard, and a highly reliable test can be performed. The purpose is to provide a concrete compression tester.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a concrete compression test apparatus according to the present invention includes a load mechanism for applying a compression load to a test concrete block, a load detection means for detecting a compression load acting on a test piece, and a load detection thereof. At least one of stress rate control for controlling the load mechanism so that the change rate of the load detection value is constant by inputting the output of the means and constant speed stroke control for maintaining the displacement rate of the load mechanism constant In a concrete compression tester equipped with a control means capable of selecting such control, during the control of the stress rate control, the output of the load detection means is taken in every moment, and the change rate of the detected value is relative to the target speed. And determining means for determining whether or not the deviation exceeds a preset limit, and the control means changes the load detection value based on the determination result. Speed is characterized by switching automatically to the constant speed stroke control control when the changes beyond the limit to the target speed.
[0007]
In the present invention, when a concrete block undergoes a sudden deformation under a stress test while the rate of change in load acting on the concrete block matches a certain target speed, By utilizing the fact that the changing speed deviates greatly from the target speed and automatically grasping the rapid deformation, the intended purpose is achieved.
[0008]
In other words, in a state where a compressive load is applied under the stress rate control, the load change rate is kept approximately the same as the target speed (target load change rate). If the load mechanism is suddenly deformed, the load mechanism cannot follow the deformation, and the load detection value by the load detecting means fluctuates abruptly, and the load changing speed deviates greatly from the target speed. This phenomenon can be grasped from the momentary output of the load detection means, and by automatically switching from the stress rate control to the constant speed stroke control at that time, the switching timing can always be made accurate. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of an embodiment of the present invention, and is a diagram illustrating a schematic diagram showing a mechanical configuration and a block diagram showing an electrical configuration.
[0010]
The testing machine main body 1 is provided with two screw rods 12a and 12b vertically on the main body frame 11, and supports both ends of the crosshead 13 via nuts on the screw rods 12a and 12b. The upper surface of the frame 11 has a structure in which a table 14 is supported so as to be movable up and down.
[0011]
The screw rods 12a and 12b are rotated by driving a motor (not shown), and the cross head 13 is moved up and down by the rotation of the screw rods 12a and 12b. As will be described later, the cross head 13 is moved up and down to adjust the distance between the upper and lower platens 16 and 17 sandwiching the specimen W. On the other hand, the table 14 moves up and down by driving a load hydraulic ram 15 housed in the main body frame 11.
[0012]
A specimen W, which is a concrete block used for the test, was placed on the platen 17 on the table 14 side, and the crosshead 13 was positioned so that the platen 16 on the crosshead 13 side was in contact with the upper surface of the specimen W. In this state, a compressive load is applied by driving the hydraulic ram 15 for loading to raise the table 14.
[0013]
The hydraulic ram 15 is driven and controlled by the pressure oil discharged from the hydraulic pump 21 a of the hydraulic unit 21 being supplied via the servo valve 22. The compressive load acting on the specimen W by driving the hydraulic ram 15 is detected by a pressure cell 31 that measures the pressure in the hydraulic ram 15. After the output of the pressure cell 31 is amplified by the load measuring amplifier 32 is constantly taken the CPU upon digitized by the A-D converter 33 to the control unit 40 mainly.
[0014]
The control unit 40 is connected with a keyboard 41 for giving various commands such as setting a load increase target value for every fixed time, which will be described later, and a recorder 42 for recording the test results. The momentary load data taken in via the device 33 is recorded in the recorder 42 as a load-time curve or the like. Further, the control unit 40 executes stress rate control for controlling the valve opening degree of the servo valve 22 so that the rate of change coincides with the above-described load increase target value using the load data taken in every moment, or A control signal is supplied to the servo valve 22 via the DA converter 34 in order to execute constant speed stroke control with the valve opening kept constant.
[0015]
FIG. 2 is a flowchart showing the contents of the control switching program installed in the control unit 40. Hereinafter, concrete compression based on the JIS A1108 standard according to the embodiment of the present invention will be described with reference to this figure. The operation procedure during the test will be described.
[0016]
Prior to the test, a target value P ₀ of the load increase rate during stress rate control is set from the keyboard 41. The set target value P ₀ is converted into a preset minute time, for example, a load increase target amount P per 100 ms, and stored in the memory.
[0017]
When the start of the test is commanded, the hydraulic ram 15 is driven by constant speed stroke control and the table 14 is raised at a constant speed until the value of the load data taken every moment reaches a specified value, for example, 1% of the full scale load. Then, the program shifts to stress rate control, and the program of FIG. 2 is executed while the stress rate control is being performed.
[0018]
Now, during the stress rate control, the valve opening of the servo valve 22 is controlled momentarily so that the load data value taken in every moment increases at the target value P ₀ of the load increase rate. After reaching a predetermined value, for example, 7% of the full scale load, the latest load data is read every 100 ms, the latest load data L1 and the previous load data L2 read 100 ms before (L1−L2) and a target load increase amount P per 100 ms, and whether or not both are different from each other over a preset specified value ε, that is,
| (L1-L2) -P | ≦ ε (1)
Whether or not the above is satisfied is determined. If the expression (1) is satisfied, i is set to 0 and the stress rate control is continued. On the other hand, if the expression (1) is not satisfied, i is incremented by one. When i reaches 5, that is, when (L1-L2) and P differ by more than ε for five consecutive times, the valve opening degree of the servo valve 22 at that time is constant from the stress rate control. Automatically switches to the constant speed stroke control.
[0019]
According to the above operation, it can be surely detected that the specimen W has suddenly deformed, and the stress speed control is always automatically switched to the constant speed stroke control at an accurate time. That is, when the specimen W suddenly compresses and deforms under stress rate control, the load acting on the specimen W, and hence the value of the load data by the pressure cell 31, is abrupt regardless of the control of the hydraulic ram 15 by the servo valve 22. The increase amount (L1-L2) of the load data in 100 ms deviates significantly compared to the target amount P (usually significantly smaller than the target amount P). In this embodiment, in consideration of fluctuations in load data due to disturbances and the like, control is performed assuming that rapid deformation of the specimen W occurs when the above-described fluctuations in load speed occur five times in succession. Is automatically switched from the stress rate control to the constant stroke control, the control is always switched at a stable and accurate time.
[0020]
In the above embodiment, the control is switched when the difference between (L1-L2) and P continues five times continuously. However, the number of times is arbitrary, and the influence of disturbances, etc. It can be set to any number of times after consideration. In the above embodiment, the load data is read every 100 ms, and the difference between the latest load data L1 and the load data L2 read before that is compared with the target amount P. Of course, it is not limited to 100 ms and can be arbitrarily set.
[0021]
【The invention's effect】
As described above, according to the present invention, it is automatically confirmed that the detected value of the load acting on the specimen shows a sudden change in a state where a compressive load is applied to the concrete block in the stress rate control state. The conventional test equipment that automatically switches from stress rate control to constant speed stroke control based on visual judgment by the tester as in the past. Compared to the above, it is possible to always make the control switching time accurate, there is no possibility of human error or operation error, and the accurate test result can always be obtained. Moreover, since the control of the concrete compression test is fully automated, labor required for the test can be reduced.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an embodiment of the present invention, and is a diagram illustrating a schematic diagram showing a mechanical configuration and a block diagram showing an electrical configuration.
FIG. 2 is a flowchart showing the contents of a control program installed in the control unit 40 according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Test machine main body 11 Main body frame 12a, 12b Screw rod 13 Cross head 14 Table 15 Hydraulic ram 16, 17 Platen 21 Hydraulic unit 21a Hydraulic pump 22 Servo valve 31 Pressure cell 32 Load measurement amplifier 33 AD converter 40 Control part 41 Keyboard 42 Recorder W Specimen (concrete block)

Claims (1)

A load mechanism for applying a compressive load to the concrete block to be tested, a load detecting means for detecting a compressive load acting on the test piece, and an output of the load detecting means is input, and the rate of change of the load detection value is constant. In a concrete compression testing apparatus provided with a control means capable of selecting at least one of stress rate control for controlling the load mechanism and constant speed stroke control for maintaining the displacement rate of the load mechanism constant. During the control of the stress rate control, the output of the load detecting means is taken in every moment, and the discrimination for determining whether the change rate of the detected value has deviated beyond the preset limit with respect to the target speed And the control means automatically performs control when the change speed of the load detection value changes beyond the limit with respect to the target speed based on the determination result. Concrete compression test apparatus characterized by switching the constant speed stroke control manner.

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